The present invention relates to a developer cylinder and drive gear arrangement used with a developer-replenishing device in a copier, facsimile apparatus, printer or similar electrophotographic image forming apparatus.
FIG. 1 shows a developer cylinder and drive gear arrangement used in the developer-replenishing device of a copier, facsimile apparatus, printer or similar electrophotographic image forming apparatus. This arrangement comprises a drive gear A, and a developer cylinder E driven by the drive gear A. The drive gear A has a gear shaft B at its center. The gear shaft B has a twisted triangular coupling hole C axially disposed on its one end. The developer cylinder E is fixedly mounted with a transmission gear F, and has a twisted, triangular coupling block D axially raised from its one end for coupling to the coupling hole C at the gear shaft B of the drive gear A. Because the developer cylinder E wears quickly with use, it must be replaced when starting to wear. However, the developer cylinder E is not inexpensive. Because the triangular coupling block D is twisted in one direction, its fabrication is complicated, thereby rendering a high manufacturing cost.